From a0ee77202c35dc784442f68eb14bf20b8144a872 Mon Sep 17 00:00:00 2001
From: Enginex0 <enginex0@users.noreply.github.com>
Date: Tue, 10 Mar 2026 14:23:33 +0100
Subject: [PATCH] fix(attestation): correct leaf CN casing and enforce
 keystore2 parameter policy
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Leaf cert Subject CN used "KeyStore" (capital S) but AOSP
KeyGenParameterSpec uses "Keystore" (lowercase s). Fixed in both
the Rust native certgen and BouncyCastle paths.

Replicate keystore2's security_level.rs parameter validation for
software-generated keys: reject CREATION_DATETIME (output-only tag,
ResponseCode 20) and device ID attestation tags (CANNOT_ATTEST_IDS
-66) that real keystore2 blocks before they reach the HAL.

Also fix createErrorReply parcel write order — AIDL protocol expects
exception_code, message, error_code but we had message and error_code
swapped, causing malformed replies for positive error codes.
---
 .../interception/keystore/InterceptorUtils.kt      |  2 +-
 .../shim/KeyMintSecurityLevelInterceptor.kt        | 14 ++++++++++++++
 .../TEESimulator/pki/CertificateGenerator.kt       |  2 +-
 native-certgen/src/certbuilder.rs                  |  2 +-
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/app/src/main/java/org/matrix/TEESimulator/interception/keystore/InterceptorUtils.kt b/app/src/main/java/org/matrix/TEESimulator/interception/keystore/InterceptorUtils.kt
index d187f1e..bbfaeb4 100644
--- a/app/src/main/java/org/matrix/TEESimulator/interception/keystore/InterceptorUtils.kt
+++ b/app/src/main/java/org/matrix/TEESimulator/interception/keystore/InterceptorUtils.kt
@@ -17,8 +17,8 @@ object InterceptorUtils {
     fun createErrorReply(errorCode: Int): BinderInterceptor.TransactionResult.OverrideReply {
         val parcel = Parcel.obtain().apply {
             writeInt(EX_SERVICE_SPECIFIC)
-            writeInt(errorCode)
             writeString(null)
+            writeInt(errorCode)
         }
         return BinderInterceptor.TransactionResult.OverrideReply(parcel)
     }
diff --git a/app/src/main/java/org/matrix/TEESimulator/interception/keystore/shim/KeyMintSecurityLevelInterceptor.kt b/app/src/main/java/org/matrix/TEESimulator/interception/keystore/shim/KeyMintSecurityLevelInterceptor.kt
index 30fe8e6..aadcad8 100644
--- a/app/src/main/java/org/matrix/TEESimulator/interception/keystore/shim/KeyMintSecurityLevelInterceptor.kt
+++ b/app/src/main/java/org/matrix/TEESimulator/interception/keystore/shim/KeyMintSecurityLevelInterceptor.kt
@@ -254,6 +254,18 @@ class KeyMintSecurityLevelInterceptor(
                     return InterceptorUtils.createErrorReply(KEYMINT_INVALID_INPUT_LENGTH)
                 }
 
+                if (params.any { it.tag == Tag.CREATION_DATETIME }) {
+                    SystemLogger.warning("[TX_ID: $txId] Rejecting CREATION_DATETIME in generateKey params")
+                    return InterceptorUtils.createErrorReply(RESPONSE_INVALID_ARGUMENT)
+                }
+
+                if (parsedParams.serial != null || parsedParams.imei != null ||
+                    parsedParams.meid != null || parsedParams.secondImei != null ||
+                    params.any { it.tag == Tag.DEVICE_UNIQUE_ATTESTATION }) {
+                    SystemLogger.warning("[TX_ID: $txId] Rejecting device ID attestation for uid=$callingUid")
+                    return InterceptorUtils.createErrorReply(KEYMINT_CANNOT_ATTEST_IDS)
+                }
+
                 val keyId = KeyIdentifier(callingUid, keyDescriptor.alias)
                 val isAttestKeyRequest = parsedParams.isAttestKey()
 
@@ -515,6 +527,8 @@ class KeyMintSecurityLevelInterceptor(
         // Binder buffer is ~1MB; 256KB provides 4x safety margin for transaction overhead
         private const val MAX_ALIAS_LENGTH = 256 * 1024
         private const val KEYMINT_INVALID_INPUT_LENGTH = -21
+        private const val RESPONSE_INVALID_ARGUMENT = 20
+        private const val KEYMINT_CANNOT_ATTEST_IDS = -66
         private const val MAX_CONCURRENT_HW_KEYGEN_PER_UID = 2
         // Sliding window: max hardware keygen permits per UID within the burst window
         private const val MAX_HW_KEYGEN_PER_WINDOW = 2
diff --git a/app/src/main/java/org/matrix/TEESimulator/pki/CertificateGenerator.kt b/app/src/main/java/org/matrix/TEESimulator/pki/CertificateGenerator.kt
index a5b3517..63c4c70 100644
--- a/app/src/main/java/org/matrix/TEESimulator/pki/CertificateGenerator.kt
+++ b/app/src/main/java/org/matrix/TEESimulator/pki/CertificateGenerator.kt
@@ -213,7 +213,7 @@ object CertificateGenerator {
         uid: Int,
         securityLevel: Int,
     ): Certificate {
-        val subject = params.certificateSubject ?: X500Name("CN=Android KeyStore Key")
+        val subject = params.certificateSubject ?: X500Name("CN=Android Keystore Key")
         val leafNotAfter =
             (signingKeyPair.public as? X509Certificate)?.notAfter
                 ?: Date(System.currentTimeMillis() + 31536000000L)
diff --git a/native-certgen/src/certbuilder.rs b/native-certgen/src/certbuilder.rs
index 77d87a8..d87b7a2 100644
--- a/native-certgen/src/certbuilder.rs
+++ b/native-certgen/src/certbuilder.rs
@@ -51,7 +51,7 @@ fn build_leaf_cert(
     let subject_dn_der = if let Some(ref subject) = params.cert_subject {
         subject.clone()
     } else {
-        encode_simple_cn_dn("Android KeyStore Key")
+        encode_simple_cn_dn("Android Keystore Key")
     };
 
     // Validity